1. Field of the Invention
The present invention relates to an apparatus and method to operate a liquid crystal display (LCD), and more particularly, to an apparatus that rejects an error due to noise in a digital image signal to improve a response speed of an LCD, and a method therefor.
2. Description of the Related Art
As size and weight of personal computers (PCs) and televisions (TVs) reduce continuously, light and compact displays devices have been developed. As a result, flat-panel type displays such as liquid crystal displays (LCDs), have appeared and are replacing the conventional cathode ray tubes (CRTs).
The LCD is a display device that produces a desired image signal by applying an electric field to a liquid material that has anisotropic permittivity and is injected between two substrates. An amount of light transmitted to the two substrates is adjusted by controlling an intensity of the applied electric field.
Liquid crystals used in LCDs present a hold-type physical property. In other words, a state of the liquid crystals corresponding to current data is maintained until next data is input. A response speed of the liquid crystals indicates how fast the liquid crystals change according to input data. Most LCD panels have the response speed faster than 1/60 seconds, which corresponds to a speed of one frame per 16.6 ms. Accordingly, as shown in FIG. 1, a long period of time corresponding to several frames is necessary between intermediate levels of a general image until the liquid crystal reaches an appropriate voltage in response to the input data. For this reason, ghost, a reduction in a dynamic contract ratio, and blurring edges occur in moving-image display devices such as TVs, digital TVs or DVD players, thereby deteriorating image quality.
FIG. 2 is a block diagram of a conventional apparatus to improve the LCD response speed, which prevents deterioration of the image quality. Input digital image data is temporarily stored in a buffer 200 in conjunction with a frame memory 201. Current image data Dn stored in the buffer 200 and previous image data Dn-1 stored in the frame memory 201 are input to a comparator 202. The comparator 202 compares a gradation of the current image data Dn and a gradation of the previous image data Dn-1 at a same pixel position. If the gradation of the current image data Dn and the gradation of the previous image data Dn-1 are the same, the comparator 202 outputs data Dn′ that has a response speed of the gradation of the current data Dn. If the gradation of the current image data Dn is larger than the gradation of the previous image data Dn-1, the comparator 202 outputs the data Dn′ that has a gradation larger than that of the current data Dn. On the contrary, if the gradation of the current image data Dn is smaller than the gradation of the previous image data Dn-1, the comparator 202 outputs the data Dn′ that has a gradation smaller than that of the current data Dn. A controller 203 controls reading or writing data from or to all blocks.
However, the use of the apparatus to improve the response speed of FIG. 2 leads the LCD to be sensitive to every kind of noise. In this case, noise on a screen, which is not serious in the LCD having slow response speed, grows worse after improving the response speed, thereby causing serious deterioration of the image quality.